For example, patent literature 1 discloses a configuration in which multiple antenna elements operating at different frequency bands are disposed on a ground plate having a planar shape in a standing manner adjacent to one another.
However, in the configuration disclosed in patent literature 1, induced currents having current vectors in opposite directions are generated in the antenna elements disposed adjacent to one another by a coupling of the antenna elements disposed adjacent to one another. As a result, a gain of the antenna element is decreased caused by the flow of the induced current, and a desired directivity and a desired gain of the antenna element cannot be acquired.